The applicants' French patent No. 2 608 484 describes a laser microbeam machine for performing, in particular, very fine and very accurate cutting operations of thin films of material, for correcting microdefects in electronic circuits, for repairing them, for reconfiguring them, for performing microanalysis thereof, etc. This machine essentially comprises: a laser source such as a continuous argon laser; an optical system for transmitting the laser beam emitted by the source to the objective lens of a microscope pointing towards the object to be treated; and means for supporting the displacing said object along three perpendicular axes. This machine also has the advantage of enabling the work of the laser microbeam on the object to be treated to be observed continuously on a video screen.
such a machine could also be used for chemically etching or depositing material on a thin film of material, by applying the principle described in U.S. Pat. No. 4,340,617. According to this principle, a laser beam is applied to a thin film of material lying in a suitable reactive gas, preferably at low pressure. The heat given off at the point of impact of the laser beam, and the flux of photons give rise respectively to a chemical reaction between the material of the thin film and the reactive gas, and to a chemical reaction within the gas, thereby giving rise to etching and deposition of material localized at the point of impact of the laser beam.
Since the thin film object must be placed in a reactive gas at low pressure, it may be placed in a sealed reaction chamber or box of small volume having one face containing a window which is transparent to the laser radiation, with the box then being closed, a vacuum being established therein, and then the reactive gas being inserted therein at the desired pressure. In practice, the laser-passing window must be relatively large in area so as to make it possible to act over all of the surface of an electronic circuit, or nearly all of its surface, and the thickness of the window must be sufficient to withstand pressure variations of about 1 atmosphere (10.sup.5 Pa).
This relatively large thickness of transparent material gives rise to two major drawbacks:
it fixes a minimum distance between the surface of the object to be treated and the tip of the microscope objective lens used for focusing the laser beam; and
it degrades the optical qualities of a very small diameter laser beam very considerably.
Such a reaction chamber can therefore only be used with a microscope lens having relatively low magnification power and the diameter of the laser beam cannot be reduced to values of about 1 micron which would otherwise enable very fine and very accurate work to be performed.
In order to avoid this drawback, a machine has been proposed in which the thin film object is not enclosed in a sealed box, but is merely placed on a support beneath the microscope lens and surrounded by concentric zones, the first of which is connected to a supply of reactive gas while the subsequent zones are connected to sources of suction. In this way, the laser beam passing through the microscope lens arrives directly on the thin film of the object without going through a window, and the object is in a localized environment of reactive gas which is dynamically isolated from the surrounding atmosphere by the concentric annular suction zones.
However, this known prior technique does not enable the pressure and the composition of the reactive gas over the working zone to be properly mastered, nor does it make it possible to work at low pressure which is essential for good quality etching or deposition of substance on the thin film of the object.
In addition, since the reactive gas is generally toxic or explosive, the safety of personnel operating on the machine becomes a problem.
An object of the invention is to provide a simple and effective solution to these various problems.
Another object of the invention is a machine for chemically etching and depositing material on a thin film object by means of a very fine laser microbeam, having a diameter of less than a micron, for example.
Another object of the invention is a machine of this type in which it is possible to control the pressure and the composition of the reactive atmosphere very accurately, and in which it is possible to operate at low pressure.
Another object of the invention is a machine of this type which is usable in an industrial environment.